Fluid Volume Research Articles

Dynamics of hydrogen storage in subsurface saline aquifers: A computational and experimental pore-scale displacement study

The catastrophic effects of climate change can be mitigated by transitioning to renewable energy sources such as wind, solar, and hydropower while utilizing hydrogen (H2) as an energy carrier. As renewable fuel sources are intermittent and location-specific, large-scale, long-term storage options for H2 must be explored with high necessity. Subsurface hydrogen storage in saline aquifers provides a vital scope to store H2 gas in available pore voids with minimal environmental risk. In this work, a highly heterogeneous porous micromodel was used to study the immiscible two-phase dynamics at high-temperature, high-pressure saline aquifer conditions using computational fluid dynamics (CFD) simulation based on volume of fluid (VOF) method. A set of microfluidic experiments were carried out under atmospheric conditions to validate the numerical model. The VOF model was observed to show good agreement with microfluidic experiments. An unstable displacement pattern with viscous fingering was observed during various flow conditions that captured high pressure (15 and 25 MPa) and temperature conditions (323 and 343 K). It was observed that fingering displacement of brine limits the storage spaces for hydrogen, which consequently follows the high permeable path. As a result, only 0.272 fraction of brine was invaded by the H2 at a temperature of 323 K and pressure of 15 MPa. A comparison between H2-brine and nitrogen (N2)-brine flow dynamics revealed a 46% less storage capacity of porous media for H2. Formations bearing high temperature (343 K) showed an 11.27% increase in H2 storage capacity, while pressure increase had negligible effect. At low capillary number (Ca), more snap-off effects resulted in higher trapping of H2 gas. This study aims to provide meaningful insights into the complexities of flow dynamics and displacement patterns that are crucial for optimizing hydrogen storage efficiency in saline aquifers and for potential ‘white’ hydrogen production.

Daily weight monitoring for inpatients receiving chemotherapy.

Unlike intake and output documentation, which is often inaccurate and inconsistent, daily weight measurement is a reliable method to assess fluid volume status. Daily weight assessment and monitoring are crucial for preventing volume overload in patients receiving chemotherapy in the inpatient setting.

Lower vs higher fluid volumes in adult patients with sepsis - “an updated systematic review with meta-analysis and trial sequential analysis”

Lower vs higher fluid volumes in adult patients with sepsis - “an updated systematic review with meta-analysis and trial sequential analysis”

RANSE simulations for unmanned sailboat performance prediction: Coupling aerodynamics and hydrodynamics in self-sailing

During the design phase of sailboats, naval architects typically employ hydrodynamic and aerodynamic models of the sailboat, utilizing a Velocity Prediction Program (VPP) to solve the equations of motion, thus determining the sailboat's speed and performance. Traditional methods for solving sailboat motion equations often employ simplified empirical formulas or costly experimental procedures, which yield less accurate results. This study presents the RANSE-based CFD software STAR-CCM + to comprehensively model the sailboat's hull-sail-rudder assembly. By implementing overset grid technology and the Volume of Fluid (VOF) model, the paper aims to couple the solution of aerodynamic and hydrodynamic forces under wind influence and introduces PID rudder control technology to maintain a balance of forces and convergence of motion state. This approach enables the prediction of the sailboat's speed and performance, such as yaw angle, heel, and rudder angle. Results demonstrate minimal variations in sailboat speed (<0.05 m/s) and heading (<0.1°) in upwind, downwind and reaching sailing conditions, underscoring the method's feasibility and advocating for further research into self-sailing performance.

Understanding dilution effects on particle-containing pesticide droplets deposition on rice leaf via developing CFD-VOF-DPM model.

Pesticide dilution is one of the essential aspects of plant protection. However, the effect of dilution on the deposition characteristics of pesticide droplets containing particulate additives on crop leaf surfaces remains unclear and warrants further research. Herein, a validated computational fluid dynamics (CFD)-volume of fluid (VOF)-discrete phase model (DPM) numerical model was developed to analyze the influence of particle content on the deposition behavior of droplets on the leaf surface comparatively, taking into account the particle content of different diluted thifluzamide solutions. Additionally, the study aimed to analyze further the kinetic behavior of pesticide droplets landing on rice leaves across different dilution conditions. Pesticide droplets diluted 100-fold had a lower retraction rate during spreading than particle-free droplets, so the solution is more easily deposited in the leaves. Moreover, the low dilution (high concentration) increased the critical adhesion rate between droplets and rice leaves, inhibiting the bouncing of droplets on the leaf surface, thus promoting their effective deposition on the surface. In addition, low dilution (high concentration) is not conducive to spreading droplets when the impact velocity is high, and it also results in a large amount of pesticide use. The actual application process can be through understanding the dilution factor of the configured pesticide solution, and reasonable adjustment of the nozzle pressure can effectively improve the utilization rate of pesticides and reduce the pollution brought by pesticides to the environment. These results provide an essential reference for studying pesticide droplet deposition characteristics, including rice plant protection and spraying technology. © 2024 Society of Chemical Industry.

Effectiveness of Mannitol Use on Clinical Outcomes of Severe Traumatic Brain Injury Patients

Background Head injuries are considered as a silent epidemic due to the high incidence rate throughout the world. The main cause of morbidity and mortality in patients with head injury is cerebral edema which is defined as abnormal fluid accumulation in the brain parenchyma. Mannitol is a hyperosmolar solution given to reduce fluid volume in the brain. Increased high intracranial pressure can affect prognosis and can be evaluated by assessing clinical outcomes in patients with severe traumatic brain injury using the Glasgow Outcome Discharge Scale (GODS) instrument. Methods Observational analytical study with a cross sectional design on 50 patients with severe traumatic brain injury at dr. Zainoel Abidin General Hospital Banda Aceh to determine the effect of mannitol use on the clinical outcomes of severe traumatic brain injury patients which used t test analysis. Results The mean value of the group that received mannitol had a higher GODS score than the group that did not receive mannitol. The results of the T test between groups obtained a p value of 0.000 which is smaller than 0.05, so it can be concluded that the use of mannitol has an effect on the GODS score in Severe traumatic brain injury patients. The results showed that the mean GODS value in patients who received mannitol was higher than those who did not receive mannitol. Conclusion This concludes that the administration of mannitol is effective in improving the clinical outcomes of patients with severe traumatic brain injury at dr. Zainoel Abidin General Hospital Banda Aceh.

Numerical Analysis of Dual Droplet Simultaneous Oblique Impact on a Water Film

The simultaneous oblique impact of multiple droplets on a liquid film is an intricate phenomenon prevalent in diverse natural and industrial processes. However, previous studies have primarily focused on single droplet impact, while an in-depth understanding of the more complex multi-droplet scenario remains lacking. The current study aims to numerically investigate the simultaneous oblique impact of two droplets on a water film using a three-dimensional Volume of Fluid (VOF) model. The effects of the Weber number and the impact angle on the crown behavior are carefully analyzed. The results demonstrate that increasing the Weber number enhances the central uprising sheet height but has minor influences on the upstream crown radius and central sheet radius. In contrast, the increase in the impact angle leads to a decreased upstream crown radius and an increased central sheet radius, while the central sheet height remains relatively unaffected. In addition, the splashing threshold for the dual droplet impact cases is significantly lower than that of the single droplet impact cases due to the interactions between the adjacent crowns. The present results provide novel insights into the underlying physics and useful supports in developing predictive models for the intricate multi-droplet impact phenomenon.

Magnitude and associated factors of intra operative hypothermia among pediatric patients undergoing elective surgery atXX Comprehensive Specialized Hospital 2023: prospective observational cross sectional study Tigray, Ethiopia

Background: Hypothermia is characterized by a drop in core body temperature of less than 36 °C. It occurs frequently throughout the operating period and affects surgical patient outcomes differently in terms of morbidity and mortality. Because of coagulopathy, metabolic acidosis, multiple organ failure, hemodynamic instability, and infections, a core temperature below 34 °C is strongly associated with mortality. Objective: This study aimed to assess the magnitude and associated factors of intra-operative hypothermia in pediatric patients undergoing elective surgery at the Ayder Comprehensive Specialized Hospital. Method: A prospective observational cross-sectional study was conducted on 399 pediatric patients undergoing elective surgery at Ayder Comprehensive Specialized Hospital in Tigray, Ethiopia, from May 1, 2023, to July 30, 2023. Participants in the study were selected by a systematic random sampling technique. The data collection procedure was chart review and intra-operative temperature measurement, and the collected data were analyzed by SPSS version 23. The independent variables were analyzed using binary and multi-logistic regression. The odds ratio, 95% confidence interval, and p-value of &lt;0.05 were considered statistical significance. Result: The magnitude of intra-operative hypothermia was 52.9%. Neonate and infant [AOR: 6, 95% CI: 3.7, 9.8], (AOR=4.5, 95% CI: 2.9, 7) respectively, volume of fluid administered greater than half liter [AOR: 4.37, (95% CI, 3, 6.4)], patients who underwent surgery during the morning [AOR: 5.3, (95% CI: 3.8, 7.4)], and duration of surgery and anesthesia greater than 120 minutes [AOR: 2.7, (95% CI, 1.8, 4)] and (AOR=3.4, 95% CI, 2.4, 4.9], respectively, were factors significantly associated with intra-operative hypothermia. Conclusion and Recommendation: This study revealed a high magnitude of intraoperative hypothermia among pediatric patients. Being neonates and infants, having a cold volume of IV fluid administered greater than half a liter, entering surgery during the morning, the duration of surgery, and the anesthesia time were significantly associated with intra-operative hypothermia. We would like to advise anesthetists to use warm intravenous fluids, calculate IV fluids, and maintain room temperature.

Impact of magnetic data collection prior to electroanatomic model creation on acute outcomes in de novo AF procedures

Abstract Background As ablation and electroanatomical mapping technology evolve, workflows change to maximize the impact on procedural efficacy, safety, and efficiency. In a magnetic-primary navigation mode, optimization of the magnetic-impedance field links (VoXels) must be considered to provide accurate environments for anatomic modeling, mapping, and lesion placement. To achieve this accuracy and optimize speed of data collection, many operators have adopted the strategy of collecting VoXels using an ablation catheter prior to introduction of a multipolar mapping catheter. However, the impact of this workflow on procedural metrics has not yet been quantified in a multicenter, international cohort. Objective Assess the impact of optimizing the magnetic navigation field using an ablation catheter prior to collecting left atrial (LA) data using a high-density diagnostic tool on acute outcomes in de novo atrial fibrillation (AF) ablation procedures. Methods Acute observational data from 199 de novo pulmonary vein isolation (PVI) cases was prospectively collected from 56 operators at 42 centers in Europe, the US, and Australia. Procedural metrics, modeling workflow, ablation technology used, and acute outcomes were collected. Results Of 199 de novo AF (62.3% PAF) ablation procedures, VoXels were collected with an ablation catheter prior to LA map collection with a multipolar catheter in 65/199 (32.7%) cases; the remainder collected with multipolar catheter first. An irrigated, contact force sensing RF ablation catheter was used in all procedures. Mean procedure duration was similar in procedures in which VoXels were collected prior to map collection (VC) compared to those that did not (nVC) (107.0±46.8 min and 115.4±59.2 min, respectively (p=0.28)). Mean fluoroscopy time was significantly reduced in VC cases compared to nVC cases (3.0±4.5 min and 5.3±5.6 min, respectively (p=0.002)). Total RF duration was significantly reduced in VC cases compared to nVC cases (904±444s and 1063±632s, respectively (p=0.04)). There was also a significant reduction in fluid delivered through the ablation catheter in VC cases, 369±159mL, compared to nVC cases, 520±243mL (p&amp;lt;0.001). Acute success rates were similar between groups: 98.5% for VC cases and 99.2% for nVC cases (p=0.64). Conclusion In this international cohort, cases where VoXels were collected prior to map and model collection had significantly reduced fluoroscopy times, RF durations, and fluid volumes delivered through the ablation catheter, potentially as a result of improved model quality. Despite the introduction of an additional step to the workflow, there was a trend toward shorter procedures when VoXels were collected prior to map and model collection, although it did not achieve statistical significance. Better quantification of the impact of this workflow on model quality, along with analysis of long-term patient outcomes, is warranted.Procedure Duration Comparison_VC vs. nVCFluoroscopy Comparison_VC vs. nVC

An Ethical Analysis of Therapy for Severe Congenital Kidney and Urinary Tract Anomalies.

Technological advancements before and after delivery have greatly altered the counseling of pregnant patients facing a fetal diagnosis of severe oligohydramnios or anhydramnios secondary to congenital anomalies of the kidneys and urinary tract. Once considered a nearly uniformly lethal abnormality, long-term survival may now be possible secondary to prenatal innovations aimed at restoring the amniotic fluid volume and the availability of more advanced neonatal dialysis techniques. However, these available therapies are far from perfect. The procedures are onerous for pregnant patients without a guarantee of success, and families must prepare themselves for the complex life-long medical care that will be necessary for surviving individuals. Multidisciplinary counseling is imperative to help pregnant individuals understand the complexity of these conditions and assist them in exercising their right to informed decision-making. Moreover, as with any developing field of medicine, providers must contend with ethical questions related to the treatment options, including questions regarding patient-hood, distributive justice, and the blurred lines between research, innovation, and standard care. These ethical questions are best addressed in a multidisciplinary fashion with consideration of multiple points of view from various subspecialties. Only by seeing the entirety of the picture can we hope to best counsel patients about these highly complex situations and help navigate the most appropriate care path.

Physician awareness of fluid volume administered with intravenous antibiotics - a structured interview-based study.

Fluids administered as drug diluents with intravenous (IV) medicine constitute a substantial fraction of fluids in inpatients. Are physicians aware of fluid volumes administered with IV antibiotics for patients with suspected infections? Does addressing this lead to adjustments in 24-hour fluid administration/antibiotics? This cross-sectional interview-based study was conducted in three emergency departments. Physicians were interviewed after prescribing around-the-clock IV antibiotics for ³24 hours to patients with suspected infection. A structured interview guide assessed the physicians' awareness, considerations, and practices when prescribing IV antibiotics. The 24-hour antibiotic fluid volume was calculated. We interviewed 100 physicians. The 24-hour fluid volume administered with IV antibiotics was 400mL (interquartile range: 300-400). Totally, 53% of physicians (n=53) were unaware of the fluid volume administered with IV antibiotics. 76% (n=76) did not account for the antibiotic fluid volume in the 24-hour fluid administration. 96% (n=96) indicated that they would not adjust prescribed fluids after receiving information about 24-hour antibiotic fluid volume administered for their specific patient; no comorbidities associated with fluid intolerance was primary reason for not adjusting prescribed fluids/antibiotics. 79% (n=79) opted for visibility of fluid volumes administered with IV antibiotics in the medical record. The majority of physicians were unaware of fluid volumes administered as a drug diluent with IV antibiotics. The majority chose not to make post-prescribing adjustments to their planned fluid administration; they regarded their patient as fluid tolerable. The physicians opted for visibility of fluid volumes administered as diluents during the prescribing process.

#3063 MRI assessment of skin and muscle sodium (23Na) and fluid volume in haemodialysis patients

Abstract Background and Aims Haemodialysis (HD) is life sustaining for patients with end-stage kidney disease (ESKD). In healthy people, sodium balance is regulated by the kidneys; in ESKD this is achieved by sodium removal during HD. Recent evidence suggests non-osmotically stored sodium in the muscle and/or skin may be a critical factor impacting the development of hypertension and cardiovascular disease (CVD). Sodium (23Na) MRI allows skin and muscle sodium storage assessment and may provide a valuable tool in evaluating sodium storage in dialysis patients. Here, 23Na MRI is used to measure muscle and skin tissue sodium concentration (TSC) in HD participants. HD participants are scanned before and after a single haemodialysis session using 23Na MRI as well as 1H T2 relaxometry to study changes in fluid status. Method Data were collected on HD patients who underwent a pre-HD 23Na MRI calf scan, then had their usual dialysis session with a dialysate sodium of 137 mmol/L, followed by a repeat post-HD 23Na MRI scan. Patient dialysis vintage, residual renal function, and ultrafiltration volume, and blood measures pre- and post-HD were collected. 1H scans were acquired for localisation and muscle segmentation (mDIXON) along with T1 and T2 mapping. 23Na images were acquired for (TSC) quantification. Reference bottles (10, 20, 30 and 40 mmol/L NaCl) were placed above the leg to calibrate TSC muscle and skin maps. Regions-of-interest (ROIs) of each muscle group and the skin were manually segmented on mDIXON scans. In each muscle group the voxel-wise mode (to avoid influence of signals from vessels) of TSC and T2 was estimated. A paired-sample t-test was performed between metrics pre-HD and post-HD. Absolute measures of ΔTSC and ΔT2 were correlated with clinical measures. Results Ten people receiving HD were recruited (age 55-73 yrs, 5 M:5F). Figure 1 shows TSC maps of the HD patients pre-HD and post-HD, with a significant reduction (p &amp;lt; 0.05) in TSC in the extensor, peroneus and gastrocnemius muscles post-HD but skin sodium showed no detectable change. Post-HD TSC significantly positively correlated with post-HD Systolic Blood Pressure (SBP) (P &amp;lt; 0.004) but not with plasma sodium. 1H T2-maps (Fig. 2A) show a significant reduction (p &amp;lt; 0.01) in muscle T2 post-HD compared to pre-HD all muscle groups (Fig. 2B). There were no significant correlations between T2 and 23Na measures, or T2 and clinical measures. There was no significant detectable change in 1H T1. Conclusion Post-HD TSC values are consistent with published data from patients dialysed against a dialysate sodium of 137 mmol/L, and shows a significant correlation of post-HD TSC with post-HD SBP. 1H muscle T2 reduced post-HD, consistent with published data, as patients change from a pre-HD hypervolemia state closer to a post-HD to euvolemia state after fluid removal. There was no correlation of absolute or ΔTSC and 1H T2 and ΔT2 values, suggesting different mechanisms for equilibrium conditions of water and sodium ion concentrations. Future studies will study the effect of dialysate sodium on muscle TSC and mechanistic links to CVD, and include the use of a dedicated skin coil to study skin sodium alongside bioimpedance fluid measures.

Directionally‐split volume‐of‐fluid technique for front propagation under curvature flow

AbstractA directionally‐split volume‐of‐fluid (VOF) methodology for evolving interfaces under curvature‐dependent speed is devised. The interface is reconstructed geometrically and the volume fraction is advected with a technique to incorporate a topological volume conservation constraint. The proposed approach uses the idea that the role of curvature in a speed function is analogous to the role of viscosity in the corresponding hyperbolic conservation law to propagate complex interfaces where singularities may exist. The approach has the advantage of simple implementation and straightforward extension to more complex multiphase systems by formulating the interface evolution problem using energy functionals to derive an expression for the interface‐advecting velocity. The numerical details of the volume‐of‐fluid based formulation are discussed with emphasis on the importance of curvature estimation. Finally, canonical curves and surfaces traditionally investigated by the level set (LS) method are tested with the devised approach and the results are compared with existing work in LS.

#205 Features of chronic kidney disease in patients with obesity and arterial hypertension

Abstract Background and Aims to assess the indicators of composite body composition in patients with obesity and chronic kidney disease with arterial hypertension. Method 59 patients with obesity and arterial hypertension were examined. When selecting patients, inclusion criteria were taken into account: men and women aged 25 to 55 years, obesity (BMI more than 30 kg/m²; waist circumference (WC) more than 80 cm in women and more than 94 cm in men), presence of hypertension I– Stage II, grade 1–2, absence of renal pathology (history of kidney disease, structural changes in the parenchyma and vessels of the kidneys during ultrasound examination, changes in urinary sediment and urine density, proteinuria, decreased GFR less than 60 ml/min/1.73 m² ), signed informed consent. Metabolically complicated obesity was defined as the presence of abdominal obesity, a BMI of more than 30 kg/m2 in combination with hypertension and ≥ 2 cardiometabolic abnormalities. A metabolically healthy obesity phenotype was considered to be the presence of obesity without hypertension, dyslipidemia, or hyperglycemia. The results obtained during the study were compared with the indicators of a control group formed from 30 practically healthy individuals aged 25–55 years without obesity or overweight. Differences in age, gender, duration of hypertension and obesity were not established. Metabolic activity of adipose tissue was assessed by the level of leptin, soluble leptin receptors (sLR), adiponectin, resistin, free leptin index (FLI), leptin/adiponectin index (L/A). Renal function: GFR (CKD EPI and Hoek), serum and urine cystatin C, albuminuria. The composite composition of the body was studied using bioimpedance analysis using an ABC-01 Medass analyzer of body composition and balance of water sectors of the body. Results In a comparative analysis of the parameters of the composite body composition in the obese groups, the highest values ​​of fat mass (42.8 ± 6.8 and 35 ± 4.2 kg) and total fluid (40.2 ± 5.0 and 36.0 ± 2.8 kg) with a reduced proportion of 17 active cell mass (ACM) (53.0 ± 3.2 and 56.1 ± 3.4%) were detected in patients with complicated obesity (p &amp;lt; 0.05). Regardless of the obesity phenotype, correlations were established: between the level of diastolic blood pressure (DBP) and the volume of total (r1 = 0.42; r2 = 0.52) and extracellular fluid (r1 = 0.50; r2 = 0.60); level of DBP and urinary excretion of cystatin C (r1 = 0.51; r2 = 0.61) (p &amp;lt; 0.01). A decrease in the proportion of ACM in obese groups was associated with an increase in resistin levels (r1 = −0.56; r2 = −0.31). In obese groups, regardless of phenotype, fat mass was associated with leptin levels (r1 = 0.52; r2 = 0.42) and free leptin index (FLI) (r1 = 0.75; r2 = 0.46 ) (p &amp;lt; 0.05). In group 1, a positive correlation was additionally established for the volume of fat mass with systolic blood pressure (SBP) (r1 = 0.70) and DBP (r1 = 0.65), with the level of uric acid (r1 = 0.57), cholesterol LDL (r1 = 0.52), cystatin C in urine (r1 = 0.75) and insulin resistance index (HOMA-IR) (r1 = 0.65) (p &amp;lt; 0.01). Conclusion Body mass index does not determine the obesity phenotype. In patients with complicated obesity, the proportion of fat mass is higher than in metabolically healthy obesity and is associated with increased levels of glucose and uric acid. All obese patients are characterized by an increase in the percentage of total and extracellular fluid, associated with the level of blood pressure and urinary excretion of markers of tubular dysfunction.

#1319 “Peritoneal volume influence on bedside ultrasound or point-of-care ultrasonography (POCUS) volume assessment in peritoneal dialysis patients”

Abstract Background and Aims To study the variations in hydrosaline overload ultrasound parameters using PoCUS in PD patients with full and drained peritoneum and their correlation with clinical parameters. Method PoCUS and intra-abdominal pressure (IAP) measurements were performed on included patients with a full peritoneum. After drainage, a new PoCUS and a bioimpedance analysis (BIA) were conducted. Results Seventeen patients were included: 70.6% male, mean age 66 ± 9.5 years. 65% had hydrosaline overload &amp;gt;1L as assessed by BIA. The mean IAP was 15 ± 3.9 mmHg. The maximum diameter of the IVC with full and drained peritoneum was 1.44 ± 0.35 cm and 1.53 ± 0.4 cm, respectively, with no significant difference (p = 0.179). The % collapsibility of IVC with full and drained peritoneum was 49 ± 23% and 47 ± 13%, respectively, with no significant difference (p = 0.58). Kerley B-lines with full peritoneum were 1.3 ± 1.5, and with drained peritoneum were 0.71 ± 1.16, with this difference approaching statistical significance (p = 0.063). The same analyses in subgroups of patients with volume overload by BIA (OH&amp;gt;1 or OH/ECW&amp;gt;15%) did not show significant differences. In the correlation analysis of variables, IAP and peritoneal dialysis fluid volume per m2 of body surface did not correlate with the diameters or collapsibility of IVC with full or drained peritoneum. The degree of overhydration by OH (L) correlated with IVC collapsibility with drained peritoneum (Spearman ρ = −0.43; p = 0.08), as did the overhydration by OH/ECW (Spearman ρ = −0.61; p = 0.02). These correlations disappeared with full peritoneum (p &amp;gt; 0.05). The same correlation analyses were performed in subgroups of patients with volume overload by BIA (OH&amp;gt;1L or OH/ECW&amp;gt;15%) and were not significant with either full or drained peritoneum. Conclusion We did not find significant differences in the ultrasound volume overload parameters with full vs. drained peritoneum in PD patients. However, indirect data indicate a lower sensitivity of PoCUS to hydrosaline overload with a full peritoneum.

Small Hemothoraces Not Drained on Admission: Initial Volume Predicts Need for Intervention.

Unlike large hemothoraces (HTX), small HTX after blunt trauma may be observed without drainage. We aimed to study if there were risk factors that would predict the need for intervention in initially observed small HTX. A retrospective review of patients with blunt traumatic HTX from 2016 to 2022 was performed. Patients with small HTX (pleural fluid volume <400mL on admission chest computerized tomography [CT]) were included. Patients were considered as being "initially observed" if there was no intervention for the HTX within 48hours after admission. Primary outcome was any HTX-related intervention (open, thoracoscopic or percutaneous procedures) occurring after 48hours and up to 6months after injury. Univariable and multivariable statistical analyses were employed. A P-value of <.05 was considered significant. Of 335 patients with HTX, 188 (59.6%) met inclusion criteria. Median (interquartile range) HTX volume was 90 (36-134)ml. One hundred and twenty-seven (68%) were initially observed. Of these, 31 (24%) had the primary outcome. These patients had a larger HTX volume (median, 129 vs 68mL, P = .0001), and number of rib fractures (median, 7 vs 4, P = .0002) compared to those without the primary outcome. Chest-related readmission occurred in 8 (6%) with a median of 20days from injury. Of these, 7 required an HTX-related intervention. Logistic regression analysis found that both the number of rib fractures and HTX volume independently predicted the primary outcome. For small HTX initially observed, number of rib fractures and initial volume predicted delayed HTX-related intervention.

#2464 Association of vascular access flow and volume status on fistula arm by bio-impedance analysis

Abstract Background and Aims Multi-frequency bio-impedance is a tool of body composition measure and can monitor changes in extracellular volume during dialysis. Arterio-venous fistulae (AVF) could potentially affect fluid retention in the arm. We investigated whether multi-frequency bio-impedance could defect AVF stenosis or association of AVF with fluid retention in the AVF arm. Method We measured the extracellular water (ECF) and total body water (TBW) in AVF arm following hemodialysis by multi-frequency bio-impedance (Inbody S10®) using an eight-electrode contact technique. We measured AVF or AVG flow by transonic ultrasonography using an ultrasound dilution technology (HD 03®) in hemodialysis. Results Total 82 patients (male 38 patients : female 44 patients) were enrolled. The causes of ESRD were DM : non-DM = 38 : 44. The mean age of patients was 54.89 ± 13.21 years. The ECW/TBW ration of fistula arm was a significantly higher than the ECW/TBW ration of non-fistula arm (0.389 ± 0.010 vs. 0.382 ± 0.001; p&amp;lt;0.05). The ECW/TBW ration of fistula arm was a significantly negative correlation with access flow level (mL/min) on fistula (p&amp;lt;0.05). The 5kHz reactance of fistula arm was a significantly positive correlation with access flow level (mL/min) on fistula (p&amp;lt;0.05). The 5kHz Phase Angle of fistula arm was a significantly positive correlation with access flow level (mL/min) on fistula (p&amp;lt;0.05). Conclusion Absolute and also relative extracellular fluid volumes are increased in the fistula arm of hemodialysis. We thought that extracellular fluid volumes in the fistula arm were associated with access flow level (mL/min) and/or relative fistula stenosis. We suggest that multi-frequency bio-impedance can be a useful assistant tool of vascular access flow measure.

#201 Bedside lung ultrasound and bioimpedance spectroscopy for assessment of volume status in chronic kidney disease patients on hemodialysis

Abstract Background and Aims Fluid balance is important in patients with chronic kidney disease undergoing hemodialysis (HD). Majority of HD treatment incorporate a prescription for fluid removal targeted to patient's dry weight. Overestimation of dry weight causes hypertension, left ventricular hypertrophy and heart failure, while underestimation is responsible for chronic dehydration leading to the risk of hypotension. Both complications have a significant impact on the overall morbidity and mortality. Dry weight of the patient is usually assessed by using clinical parameters (edema, BP, JVP etc.), Biochemical parameters (BNP, ANP), Bioimpedance Spectroscopy (BIS) or IVC diameter and collapsibility on ultrasound (VCI index). The use of chest ultrasound to detect lung water has recently received growing attention in clinical research. Ultrasonographic lung comets (counting B-lines artifact) evaluate extravascular lung water and hence is considered as a useful tool to evaluate the hydration status of hemodialysis patients. This study aims to compare the efficacy of body fluid volume status and lung water assessment by clinical methods, Ultrasound chest and Bioimpedance Spectroscopy in chronic kidney disease patients on hemodialysis. Method A cross-sectional study was conducted over a period of 6 months. Dry weight of the patient was assessed by the attending nephrologist based on clinical criteria such as: weight, blood pressure, presence of edema or vascular congestion. A Longitudinal Ultrasound scan of the chest was performed using MicroMaxx Ultrasound System with patient in supine position from second to fourth intercostal space of left hemi-thorax and second to fifth intercostal space of right hemi-thorax along parasternal, midclavicular, anterior axillary and midaxillary lines of each side in a total of 28 sectors. B-lines were defined as hyperechogenic linear artifact emerging from the pleural line, up to the bottom of the screen. Pre and Post dialysis comet score was determined by calculating the total B-lines in each sector. Bioimpedance spectroscopy using Bodystat QuadScan 4000 was performed. Pre and post dialysis total body water (TBW), intracellular water (ICW), extracellular water (ECW) and residual fluid overload (ECW pre HD- ECW post HD) were recorded. Results We conducted 100 assessments on 34 patients presenting to the hospital for maintenance hemodialysis. The mean age of the study population was 54.3 + 11 years with a sex ratio (M/F) of 6:1. Mean systolic blood pressure was 141.1 + 19 mmHg and diastolic blood pressure was 83 + 9.3 mmHg with 3 episodes of intradialytic hypotension. The mean dry weight was 59.8 + 10 Kg and weight gain by clinical assessment was 2.1 + 1.5 Kg. Comet score assessed by ultrasound chest had a mean of 4.54 + 2.53 before dialysis and 1.73 ± 1.36 after dialysis. Residual fluid overload on Bio impedance spectroscopy was 1.11 ± 0.85 litre. The residual fluid overload on Bio impedance spectroscopy and lung ultrasound comet score after dialysis had a significant correlation (p value &amp;lt;0.0001). Of the 100 assessments, 40% had fluid overload after dialysis on Bio impedance and 35% had lung congestion on ultrasound chest even after achieving euvolemia according to the dry weight assessed clinically. Conclusion Lung comets on ultrasound chest and residual volume on bio impedance spectroscopy may precede the development of clinical sign and symptoms in a patient. Therefore, these methods are superior to clinical volume status assessment in chronic kidney disease patients on hemodialysis.

Effect of spaceflight experience on human brain structure, microstructure, and function: systematic review of neuroimaging studies.

Spaceflight-induced brain changes have been commonly reported in astronauts. The role of microgravity in the alteration of the brain structure, microstructure, and function can be tested with magnetic resonance imaging (MRI) techniques. Here, we aim to provide a comprehensive overview of Spaceflight studies exploring the potential role of brain alterations identified by MRI in astronauts. We conducted a search on PubMed, Web of Science, and Scopus to find neuroimaging correlates of spaceflight experience using MRI. A total of 20 studies (structural MRI n = 8, diffusion-based MRI n = 2, functional MRI n = 1, structural MRI and diffusion-weighted MRI n = 6, structural MRI and functional MRI n = 3) met our inclusion criteria. Overall, the studies showed that regardless of the MRI techniques, mission duration significantly impacts the human brain, prompting the inclusion of various brain regions as features in the analyses. After spaceflight, notable alterations were also observed in the superior occipital gyrus and the precentral gyrus which show alterations in connectivity and activation during spaceflight. The results provided highlight the alterations in brain structure after spaceflight, the unique patterns of brain remodeling, the challenges in drawing unified conclusions, and the impact of microgravity on intracranial cerebrospinal fluid volume.

Using the Discontinuous Bi-viscosity model to analyze the three-dimensional flow field and local scour behavior around the Claviaster libycus

Abstract Previous studies have suggested that irregular echinoids exhibit higher survival rates than regular echinoids following mass extinctions. This study focuses on the irregular echinoid Claviaster libycus, investigating its flow field and scour behavior under extreme water flow conditions through numerical simulations and experiments. The numerical model Splash3D used in this study was modified from the open-source code Truchas developed by the U.S. National Laboratory. Splash3D solves the three-dimensional incompressible Navier-Stokes Eqs.. The fluid volume method describes the water surface kinematics and sand surface kinematics. Since Claviaster libycus is semi-submerged in the sand, a discontinuous bi-viscosity model describes the rheological behavior of the bed material. The research findings indicate that when the gonopore of Claviaster libycus faces downstream, there is no evident horseshoe vortex flow, which contributes to reducing the occurrence of localized scour. This also validates the hypothesis of this study: the transition of echinoids from pentaradial symmetry to bilateral symmetry assists in stabilizing bottom sediments and reducing localized scour.